The things I did to improve were first of all play the game in a way that learning becomes the most important thing. I often notice when I am carefree and relaxed I ladder well, but when I am tense or focused on winning at all costs is when I go on tilt. If your focus is on one turn at a time, and trying to make the best play each turn, it becomes more natural to play carefully and not finish each turn like a race. I often times skype with friends and do arena, constructed, tavern brawl, etc. and we take turns spectating each other and talking about all the possible decisions you might make. It's really nice to see another person's perspective. You can also watch streams or youtube vids and pause the video and try to see if you make the same play that they do. Playing the game a lot gets you more in tune with the meta, and opening something like tempo storm meta snapshot will give you 90% of the decks you will play against. So you can look at those and get a good idea of what to expect your opponent to have in their deck. Using a deck tracker is also really helpful, I would google "hearthstone deck tracker" for the most popular one. Of course having a good deck helps, but having all the cards doesn't make you a better player.